Process of and apparatus for drying material



Aug. 16, 1932. L. B. WEST ET AL PROCESS OF AND APPARATUS FOR DRYING MATERIAL Filed March 16. 1931 2 Sheets-Sheet amnion;

Ill:

Aug. 16, 1932.

L. B. WEST ET AL PROCESS OF AND APPARATUS FOR DRYING MATERIAL Filed March 16, 1931 2 Sheets-Sheet 2.

ZZZ? PV'aZZ I abtoww Patented Aug. 16, 1932 [UNITED STATES PATENT OFFICE LAWRENCE B. WEST AND MARION r. WALL, GHATTANOOGA, TENNESSEE, ASsIGNoRs, BY DIRECT AND ME NE ASSIGNMENTS, TO THE SIMPLICITY SYSTEM COMPANY, OF

oHArrANooGA, TENNESSEE Application filed March 16, 1931. Serial No. 523,092.

This invention relates to the drying of mineral aggregate or the like under variable heat conditions and has for its object to provide an apparatus and a process which will be more efficient and less' costly to operate than those heretofore proposed. e

One object of this invention is to fprovide an apparatus that can be utilized 'or subjecting the mineral aggregate to an elevated temperature for the purpose of drying the same in a limited time.

Another object of this invention contemplates the subjection of the minerakaggregate to a combined heating and cooling action as a continuous process in'a single ap- 'A still further object of the invention resides in the provision of a singe apparatus which is suitable for either big or low temperature drying.

Referring to the accompanying drawingsforming a part of this specification in which like parts are designated by like -numerals,

Figure 1 'is a' vertical longitudinal sectional view of an apparatus made in accordance with this invention;

Figure 2 is-a transverse sectional view taken on the line 22 of Figure 1 and-looking in the direction of the arrows;

4 igure 3 's ,a transverse sectional view taken on the line 33 of Figure 1 and looking in the direction of the arrows;

Figure 4 is a perspective view of one of the flights used in this apparatus;

Figure, 5 is an enlarged sectional detail illustrating the connection between the drier cylinder and the draft chamber or breeching; and

Figures 6 and 7 are perspective views illustrating one of the deflecting plates associated with one of the compartment partitions 12 and the conical member 22.

In order that this invention may be the better understood it is said that naturally the most economical way of drying material such as mineral aggregate is to spread the material in a thin layerexposed to natural elements such as sunlight and air but, of course, this is highly impractical since the 00 time element would have tobe materially lengthened and other features such as Wind, precipitation, and humidity would be disturbing factors. Therefore, it has been an object for quite some time to devise a proce5 ess, as well as an apparatus for carrying out the process,'of drying material wherein the time element Would be shortened and the material costs would be kept within a reasonable figure in order to make the process economi- 1 cal. Whereas driers have been heretoforeproposed utilizing high temperature gases. pass ng through the device at all times counter to the flow of the material therein, de-

velopments in the treatme'ntofroad building and'other materials have recently made it necessary not only to dry the material but to discharge the material from the drier in a substantially cold condition, that is, at or near the temperature of the atmosphere. a0 Ordinarily this would necessitate a duplication of plant or the installation of so muchv additional equipment that the cost of preparing the desired material would be prohibitive. Therefore, the present invention is 86 particularly directed to the limitation of any increase "in cost of production within economical and practical bounds by the apparatus now to be described.

1 indicates any suitable furnace or source 90 of heat supply having a ilue. 65, controlled by a valve 66, at the endvof which is the annular compartment 2 communicating with the delivery chute 3. This annular compartment 2 is interposed between the flue and the 0b draft chamber 4, the latter communicating with the conduit 5 adapted to remove spent gas. In the draft chamber 4 is located an aperture 6, to the upper edge of which is hinged a flap or trap door 7, and through or screws19, of short length to which material to bedried and thereafter heated, may be introduced to the-drier by any suitable means such as the endless conveyor 8. To the draftchamber 4, and on the side thereof opposite the annular compartment 2, is secured an annular casting 9, the outer circumferential surface of which is machined for a-purpose to be disclosed later.

The draft chamber 4 is rigidly secured by the sup orting member 58 to any suitable foundat on, such as the beams59, as is clearly seen in Figures '1- and 2. I

The drier comprises the outer cylindrical casing 11 to the inner surface of which is riveted or otherwise secured a plurality of division or compartment partitions 12, the

main body portion of each extending longi tudinally approximately the entire length of the drier casing 11 andpositioned' within said drier casing 11 obliquely to a diameter passing through one of the longitudinal edges thereof as clearly illustrated in Figure 3.

Within said outer drier casing 11, and concentrically disposedthereto, is the inner tubular superheater casing 13 riveted or otherwise secured to'the inner longitudinal edges of thecompartment partitions 12 to hdldsaid superheater casing 13 in spaced relation to the drier casing 11, The superheater casing 13 is somewhat longer than the drier casing 11, and is so dimensioned'and placed that one end 14 thereof will'extend into and through the draft chamber 4, as is clearly shown in Figure 1. The other end 15 of the superheater casing 13 lies within the plane of the other, or partially closed, extremity 16 of the drier casing 11,for a purpose, as will presently appear.

Referring particularly to Figure 1, the end 14 of the superheater casing 13 is provided exteriorly with a plurality of flanges 17 'helically disposed to said superheater casing 13 to rovide a plurality of screws, or worms, 18,

' y means of which the wet material, upon entering,'the draft chamber 4 -may be moved into the drier. These screws 18, it will be observed, extend longitudinally of the superheatercasing 13, only a short distance, astheir purpose is only to move the wet material outof the draft chamber 4, and insure the material reaching the compartments formed in the drier by the partitions 12. The other end 15 of the superheater casing 13 is provided 'interiorly with a similar'set of worms,- prevent the possible collection, in large quantlties, of the material within said end. The purpose, therefore, see Figure 1, is to move the material rapidly within the superheater casing 13 from the end -15 thereof, in order that the same may positively reach the flights 20 with which the inner surface of the superheater casing 13 is provided.

' At the end 16 of the drier casing, there is provided an end plate 2'1 which forms a par cal member 22 disposed substantially concen trio with the superheater casing 13, and the smaller end of which lies somewhat within the plane of the end 15 of said superheater casing. The larger end 23 of the cone 22 is provided exteriorly with the annular flange 24, which lies in a plane parallel to and spaced from the end plate 21. Suitable supporting means are provided by which the cone 22 is secured to the ends of the compartment partitions 12. Such a means is illustrated in Figures 1, 3 and 6 wherein it will be'seen that inclined triangularly shaped deflecting plates 25 are riveted, or otherwise secured, by means of a turned over flange 251 formed thereon, to the ends of the compartment partitions 12 as is especially illustrated in Figure 6. An opposite edge 252 of the deflecting plate 25 is also provided with a flange 250, see Figures 1 and 3, by means of which said plate is riveted, or otherwise secured, to the outer surface of the cone 22. The third, or

free, edge of each plate 25 is provided-with a lip 26, obliquely disposed to the plane of {he plate 25,'for a purpose to be disclosed ater. e I

From the foregoing, and with particular reference to Figures 1 and 3, it will be seen that the hot gases from the furnace, or other source of heat supply, will leave the flue 65, and pass into the end 14 of the superheater casing 13. They will then pass longitudinally, in the direction of the arrows, through the superheater casing 13, to the other end 15'thereof, where a portion of the gases will continue in a straight path through the opening in the conical member 22. By virtue of thedraft created by the exhaust fan 67, operating back through a collector 68 connected to the conduit 5, these gases will then pass through the space between the annular flange 24 and the end plate 21, and subsequently enter the longitudinal compartments 27 formed between the drier casing 11, the superheater casing 13, and the compartment partitions 12. The gases will here unite'with other'portions of the gases. which did not pass through the cone 22, but which passed through the spaces between said cone and the superheater casing 13, as is clearly shown by the arrows in Figure 1.

The hot gases, having now arrived in the plurality of compartme ts 27, will travel therethrough, in a directi n opposite to the flow of gases, inside of the superheater casing 13, towards and through the draft chamber 4, and into the conduit 5 for ultimate discharge to the atmosphere through the usual stack 69 or other means of exitcommonly provided in apparatus of this character.

The drier casing 11 is exteriorly provided with a-plurah'ty of annular bearing rings 2'8,

which are adapted to rest on the rollers 29 suitably supported on any base or foundation such as the beams 30-, as clearly shown in Figure 1.

By so mounting the apparatus upon the free turning rollers 29, it may be rotated by any suitable means, such as the annular gear ring 31 securely attached to the exterior of the drier casing 11, and driven by the gear 32, meshin therewith andmounted on the shaft 33 a apted' to receive its power from any suitable source.

In order that gases may not escape from the apparatus, except through the upper portion of the draft chamber 4, all joints will be substantially gas tight and of any suitable well known construction. In order that the annular casting 34, carried by the drier casing 11 and rotating therewith, may move relatively to the annular casing 9, carried by the stationary draft chamber 4, and at the same time have therewith a substantially gas tight joint, it has been found advisable to machine finish the outer circumferential surface 10 of the casin 9 and the inner circumferential surface 0% the casting 34. The annular casting 34 is secured to the circular flange 35, disposed at the end 36 of the drier casing 11 and circumjacent the casting 9, by means of a plurality of bolts 37 and washers 38. Because the rollers 29 and the rings 28 associated therewith are subject to wear, the drier may become radially displaced in its relation .to the casting 9; but, in order that a substantially gas tight joint may be maintained between the casting 34 and the casting 9, it is necessary that said casting 34 shall, at all times, remain substantially concentric with the casting 9. Therefore, the annular casting 34 is not rigidly secured to the circular flange 35, but is held only loosely thereto by the plurality of bolts 37 and washers 38. In Figure 5, it will be seen that the bolts 37 are of lesser diameter than the holes 39 provided 'forthem in the annular casting 34 so that there is about each bolt 37 a space 40 of a dimension greaterthan any probable radial displacement of the drier in its relation to the casting 9. It is further seen, in Figure 5, that the bolts 37 are provided with shoulders 41, adapted to be firmly drawn against the circular flange 35 by the nut 42, and that the length of the bolt 37, from theshoulder 41 to the head 43 thereof, is slightly greater 5 than the combined thickness of the annular casting 34and the washer 38, so that there may never be a bind action between the casting 34 and the flange 35 of the drier casing 11. Furthermore, it will be seen that, due to the space 40 about each bolt 37, the annular casting 34 may, within the limits of the space 40, be readily moved in any radial direction with reference to the circular flange 34 andthe drier casing 11.

The draft chamber 4 is provided with a plurality of spindles 44, rigidly secured thereto by the collars or flanges 45 or the brackets 46, see Figures 1, 2 and 5, and said spindles are held in rigid relation to the casting 9 by the structure of the draft chamher 4 to which the casting 9 is itself rigidly secured. Each spindle-44 is provided with a journal 47 eccentrically disposed to the axis .of said spindle for a purpose presently to appear. Each spindle has, mounted upon its journal 47, a roller 48 adapted to contact the outer surface of the annular casting 34 car rled by the drier casing 11. Each spindle is further provided, at the end opposite to the journal 47 with a squared portion 49, a 7' threaded portion 50, a shoulder 51, and a nut 52. From Figure 1 it will be readily seen that, by means of the shoulder 51 and the nut 52, the spindle 44 is rigidly secured to the collar 45, or the bracket 46, see Figure 2, and, 4

therefore, to the draft chamber 4. It will, therefore, be obvious that, by loosening the nuts 52, each spindle may be loosened, with relation to the draft chamber 4, so that each spindle may be rotated, through the application of a wrench to the squared portion 49, and that, by again tightening the nuts 52, each spindle may again be rigidly secured to the draft chamber 4. Thus, it is obvious that the position of the eccentrically disposed journal 47 may be changed, by the rotation of the spindle 44, and that, therefore, one would be enabled to change the position of each roller 48 with relation to the casting 9. Thus, by means of the eccentric journals 47, can various adjustments be made as needed with the result that the annular casting 34, which, in Figures 1, 2 and 5, is seen to be guided by the rollers 48, may be correctly positioned relatively to the casting 9 secured to the draft chamber 4.

It is now seen, in Figures 1, 2 and 5, that the rollers 48 ma be accurately positioned so as to support tlie annular casting 34 in a position so nearly approaching a truly concentric relation with the casting 9 that the s ace 60, between the'annular casting 34 and t e casting 9, may be so small as to make a substantially gas tight joint, and, at the same time allow relative rotary or axial motion between the casting 34 and the casting 9, without actual contact with its resultant friction and wear taking place.

' Also, it will be seen that the drier casing clearly shown in Figure 2, so that the said material may not only flow by gravity through the aperture 6, but, by occupying the =entire space between the bottom portion of the hopper 53 and the trap door 7, prevent the entrance of any substantial amount of ail into the draft chamber 4. The material, having passed through the aperture 6, will fall upon the exterior surface of the cylindrical superheater casing 13 and will be moved, by the screws 18 on said superheater casing, from the end 14 thereof toward the compartments 27 between the superheater casing 13 and the drier casing 11. A considerable portion of the material will, through the action of gravity, slide down the inclined surfaces of the screws 18 and, therefore, be guided into the compartments 27. Other portions of the material falling too high upon the curved surface of the superheater casing 13 to slide quickly therefrom, will be carried over by said superheater casing in its rotation until finally deposited in the bottom of the draft chamber 4, but, due to the fact that the screws 18 are of such radial dimensions as to fit closely within the outer casing of the draft chamber 4, any material deposited in the bottom of said chamber will ultimately be moved, by said screws, into the drier proper, all as will be clear from Figures 1 and 2.

The material, having arrived in the end 36 of the drier casing 11, and entered the longitudinal compartments 27, will be moved toward the end 16 of said drier casing 11. That is to say, each compartment partition 12 is provided, on one side thereof, with a plurality of obliquely disposed angular cleats 54, as clearly shown in Figures 1 and 3. These cleats 54 are so mounted upon the partition wall that, as the drier rotates, said cleats will cause the material to move to the right as seen in Figure 1, in each compartment, thus insuring the travel of the material toward the end 16 of the drier casing 11. In Figure 3 it will be clearly seen that the material is divided, by the partitions 12, into a plurality of advancing streams, or, in other words, the entire bulk of material dumped into the drier is divided into substantially equal parts or streams, one stream for each compartment 27. Further, it will be observed that, as the drier rotates these separate streams of material will be much disturbed, tumbled and rolled about within each compartment 27, and will be caused to slide successively across all sides of these compartments including the side formed by the superheater casing 13.

When the material has thus progressed to the end 16 of the rotating drier, it will have reached the extreme end 15 of the superheater casing 13, and, being no longer supported by said superheater casing, the material will fall over the extreme end 15 upon the inclined surface of the conical member 22, and be propelled therefrom, under the actions of gravity,

down and into the interior of the superheater I casing 13. To facilitate the entrance of the material into the end of the superheater casing 13, as well as to prevent flow of the material from said conical surface to the bottom of the drier proper, triangularly shaped deflecting plates are provided, all as heretofore disclosed. The free edge of each plate 25 is provided with the obliquely disposed flange 26, which constitutes substantially a directing chute for the material. Especially from Figure 1 it will be seen that the material which falls upon the conical surface will slide therefrom and further, that that which slides off laterally will be caught by one of the deflecting plates 25 with the result that all of the material is positively directed into the superheater casing 13. However, to prevent an undue collecting of mater al within the superheater casing 13- at the end thereof, a screw or worm 19 is provided which is adapted to move the material quickly away from the said end 15 toward the flights 20.

These flights 20 are disposed more or less helically within the superheater casing 13, and, furthermore are staggered with relation to each other as clearly seen in Figure 1. Each flight 20 is formed with an inclined bottom portion 55, and a side 56 extending substantially radially from the superheater casing 13, as particularly illustrated in Figure 4 and in such manner as to form a pocket 57 in each flight, which is adapted to be filled with the material as the flight moves upwardly from the bottom of the rotating superheater casing 13.

However, the flights are open on the side opposite the side 55, as well as open on the side opposite the side 56, and, therefore, as the superheater casing 13 continues its rotation, the material caught in each flight 20 will fall out of the pocket 57 as the flight approaches and passes its uppermost position, as clearly shown in Figures 1 and 2. The material will thereupon drop downwardly and forwardly in a more or less divided condition and be showered across the space encompassed by the superheater casing 13, thereby exposing practically the entire surface area of the particles comprising the material to the hot gases flowing past the material. That is to say, the inclined bottom 55 of each flight 20 will cause the material, as it slides from the pocket 57 of said flight, to be directed forwardly from said flight 20, or to the left, as seen in Figure 1. Thus, it will be seen that the flights 20 not only agitate, spill and shower the ma- .terial, in the superheater casing 13, but they also cause a forward movement of the material in the said superheater casing toward the delivery chute 3.

In the foregoing it is to be observed that the direction of movement of the material through the apparatus is, at all times, counter narrate to the direction of flow of the gases. Thus the material, upon being introduced through the aperture 6 in the draft chamber 4, comes first in contact with the gases which have passed entirely through the snperheater and the drier and have been deprived therein of considerable of their original heat content. However, as the material progresses on its journey through the outer drying compartments and the inner superheating compartment, it comes progressively in contact with uniformly hotter and hotter gases, until, having progressed to the inside of the end 14 of the superheating drum 13, and being about to fall therefrom into the delivery chute 3, said material is in contact with the fresh and hottest gases entering the superheater from the flue 65. It is, thereby, seen that the coolest and wettest material is in contact only with the coolest of the gases and that the material, as it is progressively dried and heated, comes in contact with progressively hotter gases, until finally the hottest material is in contact with only the hottest gases. It is evident also, that this condition is conducive to the most rapid transfer of heat from the gases to the material and, consequently conducive to the most rapid and economical process through first drying and then heating the material.

The gases having entered the superheater casing 13 at the end 14 thereof, and, being hottest at that point, will, after traveling through the said superheater casing 13, past the conical member 22, and through the plurality of drier compartments 27, and having encountered in their passage progressively cooler and cooler material, eventually reach the draft chamber 4 and the conduit 5 at a much lower temperature.

The cool and wet material entering through the aperture 6 in the draft chamber 4, is brought into immediate contact with the outer cylindrical surface of the superheater casing 13 at the end 14 thereof, which is subjected to the highest temperature of the oncoming gases, and to the most destructive efiect thereof on the said superheater casing.

The superheater casing is thus cooled by said wet material and prevented from being injuriously overheated, as is the case in much apparatus of this character heretofore constructed. Moreover, it is to be observed that the heat thus abstracted from the cylindrical surface of the superheater casing 13 by the wet material serves to materially assist in the drying of said material.

The material fedto the drier proper, is.

the compartments 27, is brought into contact with a considerable area of the exterior cylindrical surface of the hot superheater casing 13, and, therefore, said material will absorb much heat therefrom, thereby not only greatly aiding in the drying of said material, but also aiding in the preserving of the life of said superheater casing 13.

The material, upon entering the superheater casing 13 at the end 15 thereof, by means of the conical member 22, and the deflecting plates 25, is seen to be quickly brought to the flights 20 by means of the screws 19. Having reached the flights 20, thematerial is seen to be much agitated thereby, lifted up, and cascaded therefrom in a forward direction or toward the delivery chute 3. The material is thus subjected, in the superheater to the uniformly increasingly hot gases passing through said superheater, and in such a manner that all particles of said material are many times exposed directly to the blast of said hot gases, and thereby completely superheated by the time the material reaches the delivery chute 3. It is further observed that the gases supplied through the flue may be of such temperature as will heat the material much beyond the tem erature required to drive the moisture only therefrom, so that the apparatus is thus adapted to those processes which require that material shall be heated as well as dried. It is also seen that because of the protection afforded to the superheater casing 13 by the comparatively cool material upon the exterior surface thereof, the apparatus is adapted to utilize without injury to itself, gases of much higher temperature than would be practical if the superheater casing were not so cooled.

In the usual apparatus of this character heretofore constructed, there has been a serious loss of heat from the exterior surface thereof. This invention on the other hand, avoids this serious defect by having its hottest portion, the superheated casing 13, completely surrounded by compartments or pas-= sages 27 conducting material so that any heat which may escape from said superheater casing 13 by radiation, will be captured by said material and not lost. It is further seen that the gases, by the time they have traversed the length of the superheater casing 13, entered the compartments 27, and there encountered the drier casing 11, will have been so cooled by the material in said superheater casing that they will be incapable of heating the outer casing 11 of the drier suficiently to cause any considerable loss of heat by radia' tion therefrom.

It is seen in Figure 3, that the weight of the material in the compartments 27 on the ascending side of the drier is balanced substantially by an equal Wei ht of materiallin the compartments on the escending side. But, by providing comparent partitions 12 ohthe liquely disposed as shown in said Figure 3, the material on the ascending side is directed toward the center of rotation of the drier, whereas the material on the-descending side is directed toward the outer circumference of the drier or away from the said center of rotation of the drier. This has the tendency of over-balancing the structure, and placing an increased force upon the descending side, which would normally lessen the power necessary to rotate the drier and the superheater contained therein. However, as illustrated in Figure 2, the flights 20, within the superheater casing 13, scoop material upwardly and dump the same,

while passing the vertical plane, thus adding weight to the ascending side. In practice, it is observed that there is an approximate balance of the entire device, when in full operation, whereas, if the partition plates were radially disposed to the superheater casing 13, much more power to rotate the device would be required due to the unbalanced forces.

Fitting within an opening in the plate 21 at the end 16 of the outer drier casing 11 and substantially concentrically disposed with relation to the cone 22, is a second flue 80 leading from a second furnace 81 or other suitable source of heat supply, the opening of said flue controlled as by a valve 82.

When the apparatus is used as above described for solely drying and superheating the mineral aggregate, the valve 66 will be open, the other valve 82 will be closed, and fire only in the furnace 1. When the appa ratus is used for. the combined drying and cooling of the aggregate material fire is furnished by the furnace 81 only,- with both valves 66 and 82 open whereby the hot gases from the flue 80 will enter the end 16 of the drier and be immediately directed, by the draft created by the exhaust fan 67, into and through the plurality of compartments 27 in the outer casing and ultimately reach the conduit 5. In this connection, it is to be understood that the furnacelwill be open whereby the same exhaust draft will cause air at atmospheric temperatureto pass through said furnace, through the open flue 65 and through the inner drum or casing 13 of the drier, to ultimately mix with the hot gases from the other flue 80 at the far end of said inner casing, and from this point both the relative cool air and the heated gases will travel together asabove stated to reach the conduit 5. In'both treatments of the aggre gate, i. e. drying and superheating as well as drying and cooling, the travel of the air and/or gas is always counter to the travel of the aggregate in the apparatus. The cone 22 as well as its annular flange 24 are of sufficient extension to cover the opening of the flue 80, and thus prevent material from the compartments 27 dropping into said flue opening when said material passes into the. inner drum. It will be understood that the cone 22 can be eliminated particularly in cases where the temperature of the gases entering from the flue 80 will be so high as to cause damage to such a cone, the alternative construction in such cases being to permit direct passage of said gases into the compartments 27. a

The exhaust fan 67, driven in any suitable manner, is preferably made of relatively great size and capacity (e. g. 6 feet in diameter with 1200 R. P. M.) in order to create a very substantial draft not only to overcome any leakage of air at the joints and openings of the apparatus, which is extremely small in quantity, but also to pick up the finer particles of the aggregate and separate them from the larger particles. That is to say, it is manifestly diflicult to dry finely divided material because of its compactness, the voids or spaces between the fine particles being insufficient in size to permit air circulation for drying purposes. Also, it is difficult to dry larger particles when mixed with the fine particles because the latter will fill the interstices or spaces between the former and thus prevent the circulation of the drying medium. Therefore, by this invention, the finer and larger particles are separated in the compartments 27 by the draft created by the fan 67 and carried in the gas stream through the conduit 5 to the collector 68.

This collector may be of any suitable type but preferably is of the cyclone type wherein there is provided an inner downwardly extending and centrally disposed pipe 8;) open at its lower extremity and communicating at its upper end with a second conduit 84 comprising the inlet of the fan 67, the outlet from saidfan leading directly The bottom of the collector is preferably funnel-shape, converging downwardly to a throat 85 controlled by a weighted valve 86 for automatically permitting successive discharges of the material from the collector when quantities of a predetermined weight have accumulated therein,the discharged material passing into a chute 87 leading to an endless conveyor, generally indicated by the numeral 88, which also receives the cooled and/or heated material from the chute 3 leading from the drier proper.

By this arrangement the completely dried fine and large particles are reunited for simultaneous subsequent treatment as desired.

Thus it will be seen that the exhaust draft passes through the collector and in doing so brings thereto the finer particles of the aggregate which collect therein. In traveling to said collector these particles have been subjected not only to the elevated temperatures of the drying gases but have been whirled in flurries throughout their confining chambers such as the compartments 27, breeching 4, and

to the stack 69.

conduit 5 whereby said particles, having small volume and relatively wide separation each from the other (as powder or dust), are completely dry upon reaching the collector so that they fall to the bottom thereof as will be readily understood. If necessary a fine mesh screen may be applied over the open bottom end of the pi e 83 in the collector.

From the oregoing disclosureit will thus be seen that there is provided an apparatus comprising an outer drum or casing 11, an inner drum or casing 13 concentrically and coaxially disposed relatively to eachother and secured to each other by the obliquely disposed partitions 12 having the obliquely disposed cleats 54 carried on one side thereof; Further, it will be observed that the material admitted to the apparatus through the opening 6 will contact with the outer surface of the inner drum 13 which, when the apparatus is used forthe hot process, receives the gases of highest temperature from the flue 65. The burning out of the end 14.- of the inner drum 13 is thus prevented by the wet material contacting therewith, and in fact the life of the entire inner drum is lengthened because of the material being dried disposed on the outer circumferential surface thereof, and the hot gases contacting with the inner surface thereof. Further, it will be observed that the hot gases are brought into the apparatus at its central portion, and being underan exhaust pressure, have to travel to the end 15 of the inner drum 13 before they can escape from said drum, and that upon the escape of said gases,

said pressure will cause them to flow in the direction of the arrows in the passages formed by the partitions 12 between the outer and upper drums (the valve 82 being closed) eventually escaping to the atmosphere by way of the conduit 5.

Thus the apparatus, when used for the hot process, may be considered as having two zones. The inner drum 13 in its length constitutes a high temperature zone for heating the dried material to that degree found necessary in the ultimate use of'the material. The space between the outer and inner drums, on the other hand, constitutes a relatively low temperaturezone in which such heat as remains in the gases, after their passage through the high temperature zone, is absorbed by the wet material in the passages 27 and in'which there is also transmitted to the wet material such heat as may find its way, by conduction, radiation, or otherwise, through the circumferential wall of the inner drum 13. Therefore an important feature of this invention lies in the fact that the final or high tempera ture stage of the hot process takes place in the turn such heat to the hot zone thus preventing its dissipation into the atmosphere. This makes it unnecessary in industrial processes to use recuperators, regenerators, heat ex- .changers, or other external heat recovery apparatus. In other words, the. fresh material admitted to the apparatus tends to sweep the escaping heat back into the' apparatus to be utilized therein and not lost, thus'preserving the relatively high temperature of the heating zone within the inner drum 13.

On the other hand and when the apparatus is used for the cold rocess, the wet material has the tendency o cooling the outer and inner casings resulting in a conservation of the high temperature of the gases admitted from the flue 80-and flowing under the exhaust pressure through the compartments 27 between the drums. Further, the air at atmospheric temperature admitted through the flue of the now unheated furnace 1 cools the gas-dried material so that when said material reaches the discharge chute 3 it is substantially at atmospheric temperature and ready for use, or it may be conveyed through an extended chute as shown in Figure 1 for delivery to the conveyor 88 leading to a storage receptacle or to apparatus for further treatment of said material. i

Thus it will be seen that this apparatus may be used for dual treatments of material such as mineral aggregate. The furnace 81 can be used for furnishing hot gases which will dry the material as the gas passes through the space between the drums, said gas being under sufficient force to abstract the finer parts of the material from'the aggregate and carry them through a conduit 5 to the collector 68 where they arrive-completely dried.

Simultaneously the constantly -moving stream of aggregate after passing into the inner drum isthere subjected to a draft or current of air at substantially atmospheric temperature drawn in through the furnace 1 which, of course, is devoid of fire for this treatment, and the dried aggregate is cooled during its passage through the. inner drum in contact with the current of cooling air.

.When the apparatus is used thusly, both valves 66 and 82 will be open, although the latter may be varied in its position in accordance withthe temperature of the gases desired for drying particular aggregate.

On the other hand, the furnace 1 can be used as the sole source of heat in which event the aggregate is dried and superheated before its discharge from the apparatus. For

this treatment the valve 66 can be adjusted to suit the temperature requirements of the gas according to the aggregate, or it can .be adjusted in combination with the adjustment of the valve 82 of the other furnace, which latter furnace can be utilized to temper the temperature of the gases going through the drier structure. Obviously both furnaces could be utilized as heating or cooling media. It is obvious, to those skilled in this art,

that the details of construction involving the apparatus, as well as the steps and combinations of steps constituting the process of drying, may be Varied without departing from the spirit of the invention, and there-.

efore it is not desired to be limited to the above disclosure, except as may be demanded by theclaims.

' What is claimed is '1. A method of treating material which consists in conveying the material in a cylindrical stream in one direction and then in the reverse direction within said stream, the material while moving in the first direction subjected to a current of hot gas, and said material while moving in the other direction subjected to a current of cooling air, the currents of gas and air being counter to the flow of material, and the current of gas passing through the area of change of directional flow of the material.

2. A method of treating material which consists in conveying the material in a cylindrical stream in one direction and then conveying it in the reverse direction within said stream; conducting a current of drying gas counter to the flow of material while said material is travelling in the first of said directions, said current directed through the area of the change of directional flow of said material; and then subjecting the material so dried, and while travelling in the other of said directions, to a current of cooling air.

In testimony whereof we afiix our signatures.

LAWRENCE'B. WEST, MARION P. WALL. 

